Bloom gelatin in cold water for 5 minutes until softened. In a saucepan, warm espresso with brown sugar and spices until sugar dissolves. Remove from heat, stir in melted white chocolate, and cool slightly.

In a bowl, whip mascarpone and heavy cream until soft peaks form. Fold in cooled espresso mixture gently.

Mix flour, brown sugar, ground ginger, and salt. Stir in molasses and egg yolk to form dough. Roll out and cut rounds for molds.

Spoon mousse into molds, place cookie rounds on top, tap to release air, cover, and freeze for at least 4 hours.

Heat mirror glaze to 90°F. Remove frozen domes from molds, place on wire rack, and pour glaze over tops for a glossy finish.

Let set briefly, then transfer to serving plates and garnish as desired.